ADD-ONS / SCALES

Muscle strength testing (Oxford scale)

David Goldemund M.D.
Updated on 29/12/2023, published on 16/12/2023

muscle strength testing is typically performed as part of a physical examination; it may provide information about neurological deficits.
- it may be referred to as motor testing, muscle strength grading, manual muscle testing, or any other synonyms
it is used to quantify the weakness and can be effective in differentiating true weakness from imbalance or poor endurance
strength depends on a combination of morphological and neural factors, including muscle cross-sectional area and architecture, muscle-tendon stiffness, motor unit recruitment, rate coding, motor unit synchronization, and neuromuscular inhibition

in the Oxford Scale, which is the most commonly used, the patient’s strength is rated on a scale of 0 to 5 by testing key muscles in the upper and lower extremities against the examiner’s resistance
typical muscles tested include:
- shoulder abductors
- elbow flexors
- elbow extensors
- wrist extensors
- finger flexors
- hip flexors
- knee extensors
- dorsiflexors
- great toe extensor
- plantar flexors

No muscle activation
Trace muscle activation, such as a twitch, without achieving full range of motion
Muscle activation with gravity eliminated, achieving full range of motion
Muscle activation against gravity, full range of motion
Muscle activation against some resistance, full range of motion
Muscle activation against examiner’s full resistance, full range of motion

Limitations of the grading scale

muscle tested may have no clinical relevance; it is practical to add functional testing
non-linearity (the difference between grades 3 and 4 is not necessarily the same as the difference between grades 4 and 5)
inter-rater reliability
fluctuating performance (fatigue, cooperation)

Functional testing

Functional testing typically involves assessing an individual’s ability to perform activities that reflect their muscular strength and endurance in real-life situations

grip strength test – measures the maximum isometric strength of the hand and forearm muscles (dynamometer may be used)
sit-to-stand test – assesses lower body strength by counting how many times a person can stand from a sitting position in a given time frame
squat test – assesses lower body strength by counting the number of squats a person can perform.
walking on the heels and on tiptoe tests distal strength
timed up and go (TUG) Test
- a simple and commonly used test to assess a person’s mobility, balance, walking ability, and risk of falling
- the individual sits in a chair with their back against the back of the chair
- on the command “Go,” the individual stands up from the chair, walks to a marker 3 meters away, turns around, walks back to the chair, and sits down again
- the time is measured from the start command until the individual is seated again
- in general, a time of less than 10 seconds is considered normal for healthy older adults. Times longer than 12 seconds may indicate mobility issues and an increased risk of falling
6-minute walk test (6MWT) – measures the distance a person can walk quickly on a flat, hard surface in six minutes, reflecting endurance
functional reach test
- the individual leans forward as far as possible, keeping their feet fixed on the ground. The distance between the start and end position of the fingertip is measured
- the average reach distance for healthy adults is typically ~ 10 inches/25 cm; a shorter reach distance may indicate balance problems

Dynamometer

distal strength can be measured semiquantitatively using a handgrip ergometer (or an inflated blood pressure cuff squeezed by the patient) to record grip strength
requires specialized equipment, most commonly a dynamometer, which enables more precise measurement of the force that a muscle can exert and can record changes in strength over time